1. Technical Field
The invention relates to a liquid crystal display panel and repairing method thereof, and more particularly, to a repairing system of a liquid crystal display panel capable of minimizing a defect ratio and improving a yield.
2. Related Art
A liquid crystal display (LCD) device controls the light transmittance of a liquid crystal material in accordance with a video signal to display a picture. The liquid crystal display device includes a liquid crystal display panel in which liquid crystal cells are arranged in a matrix shape, and a drive circuit that drives the liquid crystal display panel.
The liquid crystal display device is divided into two types in accordance with the electric field direction driving a liquid crystal material. For a twisted nematic (“TN”) mode, a vertical direction electric field is used and for an in-plan switch ISP mode, a horizontal direction electric field is used.
For the TN mode, the liquid crystal material is driven by a vertical electric field between a pixel electrode and a common electrode which are arranged to be opposite in an upper substrate. The TN mode has a large aperture ratio and a small viewing angle. For the IPS mode, the liquid crystal material is driven by a horizontal electric field between the pixel electrode and the common electrode which are arranged in parallel on a lower substrate. The IPS mode has a large viewing angle and a small aperture ratio.
FIG. 1 is a sectional view illustrating a liquid crystal display panel 1 of TN mode of the related art. Referring to FIG. 1, the related art TN mode liquid crystal display panel 1 includes an upper array substrate 2, a lower array substrate 32, and a liquid crystal material 52 injected into an inner space between the upper array substrate 2 and the lower array substrate 32. The upper array substrate 2 (or a color filter array substrate) includes a black matrix 4, a color filter 6, a common electrode 18, and an upper alignment film 8 which are sequentially formed on an upper substrate 2. The lower array substrate 32 includes a thin film transistor (hereinafter, referred to as “TFT”), a pixel electrode 16 and a lower alignment film 38 which are formed on the lower substrate 32.
If the liquid crystal display panel 1 is driven in an IPS mode, it may have the common electrode 18 formed on the lower substrate 32. An overcoat layer is formed on the color filter 6 of the upper substrate 2. The overcoat layer compensates a step difference of the color filter 6.
In the upper array substrate 2, the black matrix 4 is formed on the upper substrate 2 and corresponds to an area of gate lines and data lines (not shown) and a TFT area of the lower array substrate 32. The black matrix 4 prevents light leakage and absorbs an external light, thereby acting to increase contrast. A cell area is provided where a color filter 6 is to be formed. The color filter 6 is formed to extend to the black matrix 4 and the cell area is divided by the black matrix 4. The color filter 6 is formed with R, G and B filters to realize R, G and B colors. A common voltage is supplied to the common electrode 18 to control the movement of the liquid crystal material 52. A pattern spacer 13 acts to keep a cell gap between the upper array substrate 2 and the lower array substrate 32.
In the lower array substrate 32, the TFT includes a gate electrode 9 formed on the lower substrate 32 along with a gate line; semiconductor layers 14, 47 overlapping the gate electrode 9 with a gate insulating film 44 disposed therebetween; and source/drain electrodes 40, 42 formed together with a data line (not shown) with the semiconductor layers 14, 47 disposed therebetween. The TFT supplies a pixel signal to a pixel electrode 16 from the data line in response to a scan signal from the gate line. The pixel electrode 16 is in contact with the drain electrode 42 of the TFT via a contact hole. A passivation film 50 is formed between the pixel electrode 16 and the drain electrode 42 and made from a transparent conductive material with high light transmittance. Upper and lower alignment films 8 and 38 are used to align the liquid crystal material 52 and formed by applying an alignment material such as polyimide and performing a rubbing process.
If a defect is generated at each thin film of the upper array substrate 2 and the lower array substrate 32 of the related art liquid crystal display panel 1, a repair is performed by using a rework or laser. However, if a particle is soundly settled between the thin films of both the upper array substrate 2 and the lower array substrate 32, the repair may be difficult with the rework or laser.
FIG. 2 is a sectional view for explaining an alignment defect caused by particle in the air, and FIG. 3 is a photo illustrating a bright point caused by the particle upon realizing a picture.
FIG. 2 illustrates particle 55 that occurs during manufacturing process of a liquid crystal display panel 1. In the chamber within which a designated thin film is formed or in case that it is moved to a separate chamber or a third location to form another thin film, the particle 55 may be soundly settled between the thin films, e.g., the common electrode 18 and the upper alignment film 8 as shown in FIG. 2. The alignment film 8 adjacent to the particle 55 may not be uniformly rubbed in a rubbing process, thereby generating a non-uniform alignment area A. Further, a portion of the color filter is separated by a defect on the process upon forming the color filter. Accordingly, a problem that the particle is intermixed is frequently generated.
The non-uniform alignment area A generates the light leakage in the liquid crystal display panel 1, and such a light leakage intercepts a light transmittance of the liquid crystal material. As a result, a bright point appears in the liquid crystal display panel as shown in FIG. 3. A dark point is an area that appears dark in case of realizing a high gray, and a bright point is an area that appears bright by the light leakage in case of realizing a low gray. Human eyes are relatively more sensitive to the bright point than the dark point. Thus, a stricter standard applies to the bright point defect than the dark point defect in determining the quality of the panel. A liquid crystal display panel having a bright point defect may be wasted or subject to a substantially reduced marketability. Accordingly, there is a need of a repair method that substantially minimizes a defect rate of a panel caused by a bright point.